The present invention relates to a rotating electrical machine, a compressor system, and a pump system, more specifically to a rotating electrical machine including a cooler, and a compressor system and a pump system each including the rotating electrical machine.
In general, a rotating electrical machine, such as an electric motor, needs to cool a rotor and a stator, and therefore includes a cooler to cool them. A typical cooler for a rotating electrical machine cools a rotor and a stator by allowing a coolant to flow into the interior of the rotating electrical machine.
In a rotating electrical machine with a relatively large capacity including such a cooler, a coolant flows from the outside toward the inside of the rotating electrical machine into a gap (airgap) between a rotor and a stator along the axial direction, and then the coolant flows radially outward through plural ventilation ducts. In this manner, the coolant cools the interior of the rotating electrical machine. The ventilation ducts are provided in the stator at predetermined intervals in the axial direction and extend in a radial direction.
In some cases, some of the coolant flows into a flow passage provided in the rotor and extending in the axial direction, and then flows radially outward through plural ventilation ducts, thereby cooling the interior of the rotating electrical machine. The ventilation ducts of the rotor are provided at predetermined intervals in the axial direction and extend in a radial direction, as with the ventilation ducts of the stator. In some cases, the coolant that has flowed through the ventilation ducts of the rotor joins with the coolant flowing in the airgap.
The coolant that has passed through the ventilation ducts of the stator is introduced into the cooler, where heat is removed from the coolant. Thereafter, the coolant is again fed inwardly in the axial direction of the rotating electrical machine by internal fans installed at both ends of a rotating shaft of the rotor.
Air is frequently used for a coolant (primary coolant) which cools the interior of the rotating electrical machine. Air or water is frequently used for a coolant (secondary coolant) which exchange heat with the primary coolant in the cooler. The following description illustrates a case where air is used for both a primary coolant and a secondary coolant. The primary coolant and the secondary coolant will hereinafter be referred to as “internal air” and “external air”, respectively.
A typical conventional rotating electrical machine includes a stator, a rotor disposed radially inside the stator, a casing that contains the stator and the rotor, and a cooler disposed above the casing for removing heat from internal air that has cooled the stator and the rotor. A tube bundle including plural tubes through which external air flows is provided in the interior of the cooler. When the internal air passes through between the tubes of the tube bundle in the cooler, the internal air exchanges heat with the external air via the walls of the tubes, whereby the internal air is cooled.
Such a conventional rotating electrical machine is disclosed, for example, in JP 10-174369 A.
A cooler is conventionally designed based on specifications of flow-cooling parameters such as amount of heat to be removed, difference in temperatures between a coolant inlet and a coolant outlet, designed air volume, pressure loss, etc. The cooling performance for a rotating electrical machine depends on such cooler specifications. With regard to the pressure loss of the parameters, it is necessary to reduce the pressure loss of the cooler by reducing the flow resistance as much as possible to enhance the cooling performance of a cooler by increasing the flow volume of internal air. It is generally necessary to increase the flow cross-sectional area in order to reduce the pressure loss.
In the case of the above-described cooler, in order to reduce the pressure loss by increasing the flow cross-sectional area, it is required to increase the pitch of the tubes of the tube bundle. However, though the increase in the pitch of the tubes can enhance the cooling performance for the rotating electrical machine, the size of the cooler necessarily increases.